I have bought a beautiful half arab/half qh filly (8 months old) and she arrived yesterday. I have two other horses, a gelding and a 7 year old mare, who were both born on the farm. The gelding is the top dog and the mare submissive to him. I put the new filliy in the stall next to the mare. In the morning I noticed the mare glaring and lying her ears back at the baby, so I decided to see how the baby did out in the pasture with the gelding first. They got along beautifully, the gelding is very nice to the filly. This weanling in a new home and so young is very submissive.
When I decided to try and turn the mare out, she charged at the filly, chased it around the pasture in a hetic, frantic, fury...trying to attack the filly. She even chased the filly into a stall and tried to attack it. Fortunately the filly escaped and I managed to shut the door and keep the mare in.
Later I tried again, took the mare out with a halter and leadrope into the pasture where the filly and gelding were. If the filly got withing 6 feet of the mare she would lay her ears back. Twice the demure little filly tried to take a step forward and say hi and the filly lounged at her. Fortunatly I had the mare in a halter and stopped her in her tracks.
I've read dozens of articles about introducing a horse to a new herd over fences and such, and perhaps I may have rushed it. It just seems though this mare is far more interested in killing this filly than getting to know her. Clearly I cannot atempt another pasture introduction anytime soon as this filly could get seriously injured. I'm considering moving the round pen to the pasture and putting the mare in it during the day and hopefully the situation will improve, but I'm fearful it will not.
Any suggestions? I also find it odd that a female horse would be so agressive to a weanling filly.